The present invention relates to a foot switch, in particular for use in medical applications.
In the medical area, particularly in hospitals, a high degree of hygiene is demanded. Especially in operating rooms compliance with rigorous criteria for hygiene is required, in order to make sure that infectious agents are eliminated as far as possible before surgery on humans is performed. Therefore the medical instruments and measurement devices must be disinfected, so that all such germs are killed. If the disinfection is not performed properly, there is an increased risk that germs will be transferred into the bodies of the patients who are being treated. So that even relatively inaccessible parts of medical apparatus can be efficaciously disinfected, in some cases these devices must be taken apart to separate their individual components. This category includes the foot switches used to control medical equipment, the mechanical construction of which is such that parts of them are not readily accessible.
A common feature of the known arrangements is that while they are in usexe2x80x94in which regard special mention should be made of the high humidity in an operating room, which is problematic for such apparatusxe2x80x94corrosion is produced in the foot switch, in particular in the joint region. This corrosion not only interferes with operation of the switch, by causing it to become jammed and hence not fully functional, but also makes it difficult to disassemble the switch completely, so that it is inadequately disinfected.
The object of the invention is to provide a foot switch of the kind described above in which simple and effective disinfection can be carried out in all parts of the switch.
According to the present invention there is provided a foot switch for use in the control of medical apparatus comprising floor plate; a pedal that is connected to and movably seated on the floor plate by means of a joint connection; a switch element; a sensor linked to the switch element; and a repositioning means disposed between the floor plate and the pedal and operable so that an operating force must be applied to the upper surface of the pedal to produce a tilting movement of the pedal out of an initial position into an operating position in which a smaller angle is defined between the floor plate and the pedal than in the initial position and in which the sensor is activated to trigger the output of a switch pulse from the switch element; the repositioning means and the joint connection being combined into an elastic joint means.
Hence, the parts responsible for bearing and repositioning the pedal, namely the joint connection, which is typically a metallic shaft, and the repositioning device, which is typically a spring means, are combined into a single elastic joint means. As a result, the number of components that need to be disinfected is reduced. Furthermore, components susceptible to corrosion are eliminated, so that it is always possible to separate the individual components of the switch from one another, and correct operation is always guaranteed. In addition, all the parts of the switch are readily accessible and hence can be effectively disinfected. Preferably, the elastic joint means is made of a rubber material. When force is applied to the upper surface of the pedal, a switch pulse is generated and is transmitted to medical devices. The force needed for this purpose is preferably adjustable. This can be achieved by limiting the flexibility of the elastic material to various degrees, by means of an adjustment or screw means. As the material is increasingly compressed, its stiffness becomes greater and its elasticity is reduced. As a result, more force must be exerted on the surface of the pedal in order to initiate a switching process.
Furthermore, the elastic joint means can be made of a number of different materials, or of a given material with variable consistency so that its elasticity varies. When the elastic joint means is made of stiff materials, an increasing amount of force must be exerted on the surface of the pedal in order to initiate a switching process. It is also possible to adapt the shape of the material according to the desired amount of applied force: materials with a smaller cross-sectional area are less stiff. In addition, a spring means can be positioned between the floor plate and the pedal.
In order to preserve a section with large area to ensure firm connection with the floor plate and the pedal, the stiffness can be sufficiently reduced by removing some of the material in particular regions, so that the cross-sectional area is reduced only in these regions.
Preferably all the individual components of the foot switch are connected to one another by means of connecting means so constructed that the components can be separated from one another without any special tools. Hence the switch can be taken apart simply and rapidly. Especially in the difficult working conditions experienced by medical personnel, this aspect makes a substantial contribution towards effective disinfection.
To enable reliable operation of the switch even under difficult working conditions, between the pedal and the floor plate a guide device is disposed, so constructed that even if force is applied at an angle, it is possible to trigger a switch pulse. If the joint is wide enough in the direction of the axis of tilt, such a special guide device becomes unnecessary.
To make sure that the foot switch operates precisely, it is necessary for the pedal always to be in exactly the same position when it is at rest, i.e. when no force is being applied. Therefore retaining devices are provided, which can be adjusted in such a way that the resting position of the pedal is as desired by the user. When the elastic joint means is constructed as a xe2x80x9crubber blockxe2x80x9d, it can simultaneously function as such a retaining device.
So that several items of medical equipment can be controlled separately, a foot switch with several separate pedals, elastic joint means and switch elements is provided. This design saves space and therefore facilitates the user""s work. The foot switch can also be constructed with a handle so that it is easy to transport.
The switch element can be constructed in very different ways. A switching process can be transmitted by pneumatic or hydraulic means and converted by way of a pressure sensor into an electrical signal that is then sent to the medical device. A switching process can also be detected by an electrical sensor, which can operate in various ways: by capacitance, inductance, by means of a potentiometer, or by way of strain gauges mounted on a surface that can be deformed by movement of the pedal. Furthermore, an optical sensor can be used to convert a switching process into an electrical signal. In this case a tilting movement of the pedal is detected by a change in a light beam. In another embodiment, in addition to a discrete signal control (switching on and off) an analog signal control (adjustable voltage) can be provided. For this purpose the angle of the tilting movement is converted into a corresponding electrical signal. It is also possible for the surface of the elastic joint means to be provided with strain gauges arranged in such a way that a variable number thereof are stretched and compressed.
In the embodiment of the switch element with special sensors, in particular the designs with inductive and optical components, a switching process can be detected by non-contact means. An advantage of this design is that the switch element can be encapsulated.
Preferably the foot switch is made of plastic materials and/or of corrosion-resistant metal.